Problem bone health: It’s not just an issue for older women

By Elizabeth Szalay, MD, and Laura L. Tosi, MD

Younger patients are also at risk for bone health issues

Although the public certainly associates “osteoporosis” with “Grandma,” orthopaedic surgeons are becoming increasingly aware of bone health issues in young adults and even children. This phenomenon raises several challenges for the surgeons and physicians who treat younger patients.

Describing the problem
One of the challenges is selecting an appropriate term to describe the problem. Because “osteoporosis” implies bone loss, use of this term is controversial when applied to children and young adults. How can patients who have not yet achieved adult bone density “lose” what has not yet been acquired?

The term “low bone density for age,” appropriately describes a child whose dual-energy X-ray absorptiometry (DXA) scan demonstrates a Z-score more than 2 standard deviations (SD) below the age-matched mean. This term should be used instead of “osteopenia” (which, in adults, means bone density between 1.0 and 2.5 SD below that of a “young normal” adult) or “osteoporosis” (adult bone density more than 2.5 SD below the mean). The term “osteoporosis” may, however, be appropriate for children who have both low bone density and a clinically significant fracture history.

What causes it?
A second challenge is to understand the causes of low bone density in children. Why would a child have low bone density and/or high fracture risk? Physicians understand—and even expect—children with osteogenesis imperfecta (OI), commonly known as “brittle bone disease,” and children who are nonambulatory (eg, those with disorders such as cerebral palsy) to have low bone density and a high risk of fracture, but many other factors may contribute to low bone density in children.

Children who take seizure medications, stomach-acid blockers, steroids, or chemotherapy agents—as well as children with arthritis, hormonal imbalances, malabsorption, renal failure, or who have undergone transplant surgery—are at risk for low bone density.

A wide range of factors influence fracture risk in the general pediatric population. These include genetics, poor nutrition (including an inadequate dietary calcium, milk avoidance, and inadequate vitamin D), lack of weight-bearing physical activity, obesity, and high exposure to trauma.

Sex also plays a critical role in the epidemiology of fractures in children. In a Swedish study, boys were 50 percent more likely than girls to sustain at least one fracture during childhood (birth to 16 years). Physeal fractures are seen at a younger age in girls than in boys, which is consistent with the respective ages of pubertal onset, when the growth plate is known to be relatively weak.

Several authors have reported that the incidence of fractures is increasing in the pediatric population. Whether this really represents more fractures or simply improved detection of minor fractures and access to care, it underscores the need for careful evaluation of children with a history of multiple fractures. Although many children sustain at least one fracture during growth, most do not, suggesting it is not the norm for healthy children to break their bones.

Most childhood fractures occur during play and sport and result from mild or moderate, rather than severe, trauma. One study found that 66 percent of fractures sustained during growth occur in children and adolescents who have had prior fractures, suggesting that certain children may be predisposed to fracture. These individuals frequently experience the first fracture prior to age 5. A history of childhood fracture doubles or even triples the risk of additional fractures.

Evaluation and management
Evaluation of the child with a history of fractures is challenging, because no gold standard for evaluation and treatment exists. Evaluation typically begins with a careful family and medical history and a DXA scan.

Bone densitometry has been shown to predict fracture risk and reflect response to therapy in older adults, but its role in the management of children is less well defined. An expert panel convened by the International Society for Clinical Densitometry recommends densitometry for children who have a history of clinically significant fractures (defined as a long-bone fracture of the lower extremities, a vertebral compression fracture, or two or more long-bone fractures of the upper extremities). Although other methods to evaluate bone quality exist, such as quantitative computed tomography, DXA is the preferred method for children, given its wide availability, rapid scanning time, and low radiation.

Pediatric DXA scanning is best done at a facility that frequently studies children; special DXA software is necessary, and the hip scan routinely performed for older patients cannot be used in young children due to the incomplete ossification of the proximal femur. Pediatric databases must be used for interpretation, and only the Z-score (which compares an individual to sex- and age-matched controls) is considered, rather than the T-score (which compares an adult to “ideal” adult density). In addition, physicians must realize that children who are small for their age will frequently have falsely low Z-scores.

Laboratory evaluation may include hematologic and biochemical indices, erythrocyte sedimentation rate, intact parathyroid hormone, serum calcium and phosphorus, urinary calcium excretion, and screening for celiac disease. Patients should be screened for vitamin D deficiency using a serum 25-hydroxy vitamin D level. The work-up may ultimately require bone marrow aspirates, endoscopy/colonoscopy, liver biopsy, or genetic testing, but these are not routinely ordered in an otherwise healthy child. Referral to a specialist in endocrinology, gastroenterology, and/or genetics may be indicated.

Conservative management is usually recommended. This includes addressing any discovered underlying condition, supplementation with calcium and vitamin D as needed, and encouraging weight-bearing activity.

The American Academy of Dermatology recommends sunscreen use during outdoor play, which blocks vitamin D production in the skin. Very few foods naturally contain vitamin D, and, despite food fortification, it is virtually impossible to intake adequate daily vitamin D from food sources alone. Accordingly, daily supplementation with 400 international units (IUs) for babies and up to 1000 IU for children is recommended. Assessment of serum 25 OH vitamin D may reveal a need for temporary supplementation at higher doses.

Two or three 8-oz servings of dairy meet the calcium need of most children, but supplementation may be appropriate in children who have dairy allergy or aversion. High-risk activities, such as trampoline and contact sports, should be limited in children who have low bone density, while low-impact weight-bearing activity should be encouraged.

Patient, parent education
The federal government is eager to help physicians educate patients and parents about bone health. One of the newest campaigns developed by the U.S. Department of Health and Human Services is Best Bones Forever or BBF (a play on the popular phrase “best friends forever”). BBF targets girls between 9 and 14 years old.

The BBF website (www.bestbonesforever.gov) provides information about bone health, calcium intake, and the importance of eating right and being active in a fun, accessible, and interactive format. The program provides a range of free materials for children, including diaries for tracking calcium and food intake, exercises, book covers, and fun tattoos, as well as pamphlets for parents. The free pamphlet “Kids and Their Bones: A Guide for Parents” is available in several languages and offers numerous hints on natural calcium alternatives.

Putting sex in your orthopaedic practice
This quarterly column from the AAOS Women’s Health Issues Advisory Board and the Ruth Jackson Orthopaedic Society provides important information for your practice about issues related to sex (determined by our chromosomes) and gender (how we present ourselves as male or female, which can be influenced by environment, families and peers, and social institutions). It is our mission to promote the philosophy that male and female patients experience and react to musculoskeletal conditions differently; when it comes to patient care, surgeons should not have a one-size-fits-all mentality.